Hi Lee
The Vceo is the most critical parameter and represents the maximum collector to emitter voltage on the device when the base is open. In practice the base is not open in circuit so the Vcex parameter comes into play. The 21196 is specified to withstand 400V from collector to emitter when the base emitter junction is biased at -1.5V (base is lower than emitter). The PL700s you have been experimenting with have about 106 volts on the B+ and B- rails. So this is a potential of 212V that you could see from collector to emitter. You are within the static ratings.
Those are all static withstand voltages with no collector current flowing for the device, in application the devices are not static. Therefore the SOA becomes the most important parameter now that you have satisfied the basic static parameters. This is the chart in Fig 13. You will see that at 212V, the MJ21196 will survive 1A collector current for 250msec before destruction sets in (this is equivalent to a half sine wave 2 Hz signal). This is impractical. When you see 212V across the transistors, it is at the peak point of the signal and the transistor is pulling the load from the peak to the other peak so in reality you will never see that type of time-current product.
Hopefully this helps and does not confuse further.
The Vceo is the most critical parameter and represents the maximum collector to emitter voltage on the device when the base is open. In practice the base is not open in circuit so the Vcex parameter comes into play. The 21196 is specified to withstand 400V from collector to emitter when the base emitter junction is biased at -1.5V (base is lower than emitter). The PL700s you have been experimenting with have about 106 volts on the B+ and B- rails. So this is a potential of 212V that you could see from collector to emitter. You are within the static ratings.
Those are all static withstand voltages with no collector current flowing for the device, in application the devices are not static. Therefore the SOA becomes the most important parameter now that you have satisfied the basic static parameters. This is the chart in Fig 13. You will see that at 212V, the MJ21196 will survive 1A collector current for 250msec before destruction sets in (this is equivalent to a half sine wave 2 Hz signal). This is impractical. When you see 212V across the transistors, it is at the peak point of the signal and the transistor is pulling the load from the peak to the other peak so in reality you will never see that type of time-current product.
Hopefully this helps and does not confuse further.
